The inventive concept relates to the field of semiconductors, and more particularly, to phase change memory devices.
A phase change memory device, such as a Phase Change Random Access Memory (PRAM), can include a phase change material, such as a chalcogenide alloy of germanium, antimony, and tellurium, which can be used to store data by inducing the phase change material to take on a crystalline state or an amorphous state. In particular, the resistance of the phase change material can be greater in the amorphous state than in the crystalline state.
In a read operation of the phase change memory device, current can be supplied to a selected phase change memory cell whereupon different tunneling currents can develop depending on the resistance of a phase change material in the cell. A sense amplifier coupled to the selected cell can compare a reference level with a level of a sensing node which changes according to the tunneling current to help distinguish between the stored data.
The data stored in phase change memory devices can be reliable for about 60 years at temperatures up to about 85 degrees Centigrade. Errors may, however, be induced in data that is exposed to higher temperatures. For example, data that is exposed to temperatures of 105 degrees Centigrade may only be reliable for about 6 months.